Interpretive Summary: Root restricting layers in the soil limit crop production in many areas and are predominant in soils of the Southern Piedmont of the USA. These layers can be disrupted with certain tillage tools. However, the long-term effectiveness of these tools is unknown for many soils and cropping systems. We evaluated annual and less frequent use of 2 tools that disrupt the soil profile known as in-row chisel and paratillage for their effects on cotton production. We compared these to disk tillage (use of a disk harrow to invert the top 15 cm of soil) and a reduced tillage system that controlled weeds with shallow (7.5 cm below the soil surface) application of sweep plows between rows (secondary tillage). Annual in-row chisel provided the best yield and economic return over the three years of cotton production. The impact of paratillage in the fall on root restricting layers was negligible because the tillage effect was lost during the winter and spring. Tractor compaction contributed to this reconsolidation. Average annual net returns from annual in-row chisel were $439, $383 and $287 ha-1 ($179, $154, and $113 ac-1) greater than those from annual disk tillage, paratillage, and secondary tillage, respectively.

Technical Abstract:
Tillage to disrupt root-restricting, consolidated soil zones can improve rooting capacity and crop production. However these operations increase production costs because of the need for more powerful tractors and greater fuel use. We evaluated the agronomic and economic consequences of annual or less frequent soil disruption operations for cotton (Gossypium hirsutum L.) production in a conservation tillage management system on a Typic Kanhapludult.
Two soil disruption tillages, paratillage (PT) applied each fall, and in-row chisel (IC) were compared with a shallow secondary tillage (ST) system and conventional disk tillage (DT). The IC, PT and ST treatments were used annually or in the 3rd, 4th, and 5th years of the study. Lint yield with IC treatments was 15 to 20% greater than DT each year. In 1994, yield ranged from 0.53 to 0.84 Mg ha-1 (480 to 750 lb ac-1) with annual IC having better yields than annual ST or PT. In 1995, cotton yields ranged from 0.92 to 1.29 Mg ha-1 (830 to 1150 lb ac-1) with the top yield associated with current year IC application. In 1996, the fifth year of the study, no significant difference in yield was observed among tillages; however, two of the top five yields were IC treatments. For the three cotton years, annual IC plots had numerically greater yields than annual PT and ST. Yields for PT and ST were no better than those of DT. Average annual net returns from annual IC were $439, $383 and $287 ha-1 ($179, $154, and $113 ac-1) greater than those from annual DT, PT, and ST, respectively. In-row chisel appears to be a more economically viable production practice for heavy Piedmont soils with consolidated zones because of its lower energy requirement and greater cotton yield response compared to PT.